Motorized articulation for vehicle seat

ABSTRACT

A vehicle seat articulation mechanism comprising a first member intended to be connected to the seat part, a second member intended to be connected to the backrest, about an axis of articulation, reduction gearing arranged between an input member and the second member, a piezoelectric motor having a rotor connected to the reduction gearing to drive the rotation of the second member with respect to the first member through the reduction gearing, in which the reduction ratio of the reduction gearing is greater than or equal to 150, and in which the nominal rotational speed of the piezoelectric motor is less than 500 revolutions/min. Seat comprising such a mechanism.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC §371 U.S. national stage filing ofInternational Patent Application No. PCT/FR2012/050954 filed on Apr. 27,2012, and claims priority under the Paris Convention to French PatentApplication No. FR 11 54146 filed on May 13, 2011.

FIELD OF THE DISCLOSURE

The present invention relates to motorized articulations (also referredto herein as “hinges”) for a vehicle seat.

BACKGROUND OF THE DISCLOSURE

It relates more particularly to a motorized hinge mechanism connectingone part of the seat to another part of the seat, for example a backrestto a seat part.

In the known prior art, such motorized hinges comprise a DC motor,reduction gearing, and a hypocycloid mechanism, one of its side platesbeing connected for example to the backrest and the other side plateconnected for example to the seat part. The rotational speeds of suchmotors are fairly high, which requires very high reduction ratios andraises noise issues concerning the motor operation. In addition, thesize and weight of such motors are significant.

There is therefore a need for motor-reduction gear combinations whichallow reducing the noise and/or size and/or weight.

SUMMARY OF THE DISCLOSURE

The invention proposes a vehicle seat hinge mechanism adapted forconnecting a first seat element to a second seat element, said mechanismcomprising:

-   -   a first member for connection to one of the first and second        elements,    -   a second member for connection to the other of the first and        second elements, mounted to rotate about the first member on a        hinge axis,    -   reduction gearing arranged between an input member and the        second member, the reduction gearing having a reduction ratio,    -   a motor having a rotor rotatably secured to said input member of        the reduction gearing, for driving the rotation of the second        member relative to the first member through the reduction        gearing,

characterized by the motor being a piezoelectric motor.

With these arrangements, it is possible to reduce the size and/or weightand/or operating noise of such motor-reduction gear combinations.

In various embodiments of the invention, one or more the followingarrangements may be used:

-   -   the reduction ratio of the reduction gearing is greater than or        equal to 150 and the rated speed of the piezoelectric motor is        less than 500 revolutions/min, such that the motor runs at a        lower rotational speed and the operating noise can be reduced;    -   the first element is a backrest and the second element is a seat        part;    -   the maximum torque of the piezoelectric motor is greater than 1        Newton-meter, such that the torque is sufficient to drive the        hinge mechanism at a rotational speed of below 500 rev./min;    -   the hinge mechanism further comprises an elastic biasing means        adapted for applying torque in a first direction, about the        hinge axis, to the second member relative to the first member,        such that the motor can drive the hinge mechanism in both        directions of rotation, the biasing means compensating for the        effects of gravity or for the presence of a user on the seat.

According to one aspect of the invention, the reduction gearing can havea single reduction stage, which simplifies the mechanism and reduces itssize. In addition, in the mechanism, the first member may comprise afirst ring gear, centered on the main axis, the second member maycomprise a second ring gear, centered on the main axis, and thereduction gearing comprises:

-   -   a drive member rotationally guided about the main axis,        comprising an input shaft and an inclined plane having a normal        that is angularly offset relative to the main axis,    -   an intermediate transmission member having a rear plane in        sliding contact with said inclined plane, a front portion        supported by the second member, a third ring gear engaging with        the first ring gear, and a fourth ring gear engaging with the        second ring gear.

In addition, the number of teeth of the third ring gear may be less thanthe number of teeth of the first ring gear, and the number of teeth ofthe fourth ring gear differs from the number of teeth of the second ringgear.

According to another aspect of the invention, the rotor shaft and theinput member may be formed of a single piece, thus simplifying themechanism.

According to yet another aspect of the invention, the reduction gearingcan have a single reduction stage comprising a single hypocycloid stageof at least 250 teeth, thus reducing the size of the mechanism.

According to another aspect of the invention, the reduction gearing maycomprise a first reduction stage formed of a planetary gear train, and asecond reduction stage formed of a hypocycloid mechanism, thus allowingthe mechanism to use optimized technological components.

According to another aspect of the invention, the reduction gearing maycomprise a first reduction stage formed of double reduction gearing, anda second reduction stage formed of a hypocycloid mechanism, thusoptimizing the size of the mechanism.

The invention also relates to a vehicle seat comprising a hingemechanism as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, objects, and advantages of the invention will be apparentfrom the following description of four of its embodiments, given by wayof non-limiting examples, with accompanying drawings in which:

FIG. 1 is a perspective view of a seat structure comprising a hingemechanism according to a first embodiment of the invention,

FIG. 2 is a diagram showing the motor and reduction gearing in the hingemechanism of FIG. 1,

FIGS. 3 and 4 are transverse cross-sections of the hinge mechanism ofFIG. 1, respectively along lines III-III and IV-IV of FIG. 2,

FIG. 5 is a perspective view of a seat structure comprising a hingemechanism according to a second embodiment of the invention,

FIG. 6 is a diagram showing the motor and reduction gearing in the hingemechanism of FIG. 5,

FIGS. 7 and 8 are transverse cross-sections of the hinge mechanism ofFIG. 5, respectively along lines VII-VII and VIII-VIII of FIG. 5,

FIG. 9 shows a diagram representing the motor and reduction gearing in ahinge mechanism according to a third embodiment of the invention,

FIG. 10 is a transverse cross-section of the hinge mechanism of FIG. 9,and

FIG. 11 shows a diagram representing the motor and reduction gearing ina hinge mechanism according to a fourth embodiment of the invention.

DETAILED DESCRIPTION OF THE DISCLOSURE

In the various figures, the same references are used to designateidentical or similar elements.

FIG. 1 shows a seat structure comprising a hinge mechanism according toa first embodiment of the invention, the seat padding and upholstery notbeing represented in the figures. The seat structure comprises a seatpart 72, and a backrest 71 mounted on said seat part by means of a hingemechanism which allows the backrest to rotate relative to the seat partabout a hinge axis Y. In the example shown, the hinge mechanism isarranged on the right side of the seat but it could of course be locatedon the opposite side.

The hinge mechanism comprises:

-   -   a first metal member 1 to be connected to one of the elements        selected from among the backrest and the seat part, which is the        backrest 71 in the case illustrated here,    -   a second metal member 2 to be connected to the other of the        elements selected from among the backrest and the seat part,        which is the seat part 72 in the case illustrated here.

The first and second members 1,2 are mounted to be substantiallypivoting relative to one another on the hinge axis Y, this motionpossibly comprising a slight cycloid component as will be seen below.

The hinge mechanism further comprises a piezoelectric motor 30 andreduction gearing 4 to rotate the second member 2 relative to the firstmember 1. The piezoelectric motor 30 has a stator and a rotor 10 forconnection to an input member 11 of the reduction gearing, in order todrive the rotation of the second member 2 relative to the first member 1through said reduction gearing 4, the rated rotational speed of saidpiezoelectric motor being less than 500 rpm. Preferably, a piezoelectricmotor can be chosen that has a rated speed of about 200 rpm, andoptimally 180 rpm.

The reduction gearing 4 is arranged between the piezoelectric motor 30and the second member 2; the reduction gearing 4 has a reduction ratiothat is preferably greater than or equal to 150.

Advantageously according to the invention, the maximum torque of thepiezoelectric motor 30 is greater than 1 Newton-meter. Such torque ishigher than the usual torque for the motors conventionally used forthese applications. For a given power, the increase in torque allowsreducing the rotational speed and thus potentially reducing the noisegenerated, or at least the higher frequencies. Such a piezoelectricmotor 30 is used in all the embodiments detailed below.

In a first embodiment, illustrated in FIGS. 1 to 4, the piezoelectricmotor 30 and the reduction gearing 4 are arranged in an internal area 79of the backrest frame that serves as their base plate.

The reduction gearing 4 comprises a first reduction stage formed ofdouble reduction gearing 62, and a second reduction stage formed of ahypocycloid mechanism 5.

As shown in FIGS. 2, 3 and 4, the motor 30 comprises a housing 32connected to the first member, a circuit board 33, and a stator 31,capable of causing rotational movement in a rotor 10 by creatingmechanical waves of a predetermined shape created by piezoelectricelements 31 a circularly arranged facing the rotor 10. The rotor 10rotates about an axis Y2 parallel to the hinge axis Y and is coupled toan input member 11 of the reduction gearing, in particular of the firstreduction stage 62.

This first reduction stage 62 is presented in the illustrated example asa series of two parallel gear trains, with a first small diameter gear51 integral with the input member 11; this first gear 51, of axis Y2,drives a second gear 52 of larger diameter which results in a reductionof the rotational speed, for example in a ratio of about 3. The secondgear 52 is centered on an axis Y1 parallel to the hinge axis Y and isrigidly coupled to a third gear 53 of smaller diameter which in turndrives a fourth gear 54 of larger diameter, integral in rotation with adrive shaft 8 and rotating about the hinge axis Y.

The first reduction stage has for example a reduction ratio of 3×3=9.

As a variant, one or two belt-type reduction gear trains could be usedinstead of the parallel reduction gears described above.

The drive shaft 8 represents the output from the first reduction stage62 and the input to the second reduction stage formed by the hypocycloidmechanism 5. This hypocycloid mechanism 5 includes:

-   -   a first metal side plate 1′ that can be coincident with the        first member 1 or rigidly connected to the first member 1, this        first side plate 1′ having internal circular gear teeth 91,    -   a second metal side plate 2′ which can be coincident with the        second member 2 or rigidly connected to the second member 2,        this second side plate 2′ comprising a disk 90 having external        circular gear teeth 92 which engage with the internal circular        gear teeth 91 of the first side plate 1′, and the external        circular gear teeth of the second side plate 2′ having a        diameter smaller than the internal circular gear teeth of the        first side plate, for example with a number of teeth that is        lower by one,    -   an eccentric cam 9 rotatably connected to the drive shaft 8,        causing a hypocycloid motion of the second side plate 2′ such        that there is always a portion 91 a of the internal teeth 91        engaged with a corresponding portion 92 a of the external teeth        92.

Each time the cam 9 completes a revolution, the second side plate 2′ isoffset by one tooth relative to the first side plate 1′. If the camrotates in the opposite direction, the second side plate 2′ is offset inthe opposite direction by one tooth relative to the first side plate 1′.

The eccentricity ‘e’ of the cam 9 substantially corresponds to thedifference in the median diameter of said gear teeth 91,92.

In the illustrated example, the internal circular gear teeth 91 consistof 34 teeth and the external circular gear teeth 92 consist of 33 teeth,resulting in a reduction ratio of 34 for the hypocycloidal mechanism 5.

Thus, for the entire reduction gearing, a reduction ratio R is obtainedof 343 multiplied by 9 which is 306, and therefore in particular R>150.

Thus angular displacements of the backrest are obtained with an angularspeed of between 2 and 6 degrees per second.

In the illustrated example, a roller bearing type of rolling mechanism95 is placed between the cam 9 and the disk 90.

In addition, the hinge mechanism may include an elastic biasing means 7,adapted for applying torque in a first direction, about the hinge axisY, to the second member 2 relative to the first member 1. This elasticbiasing means 7 is present in the illustrated example as a torsion baranchored at one of its ends 75 in a hole 77 in the first member 1 andattached at its opposite end 76 to the second member 2A in another hole78, the left second member 2A being connected to the second member 2(right side) through the seat frame 71. The elastic biasing means 7could also be present as a spring, for example helical, placed directlybetween the first member 1 and the second member 2, arranged on theright side of the seat. Any solution for directly or indirectly applyinga restoring torque between the first member 1 and the second member 2 issuitable and is within the scope of the invention.

In the example shown, the elastic biasing means 7 exerts a torquetending to push the backrest towards the front of the seat; this torqueis added to the torque from the motor, particularly when rotating thebackrest forwards with a user on the seat, which has the naturaltendency to exert a rearward force.

In addition, when the backrest is reclined significantly rearward,gravity acts, to contribute torque which tends to rotate the backresteven further back. The elastic biasing means 7 exerts opposing torque,which can increase with the seat angle to compensate for the effects ofgravity. A slight forward bias may be arranged for when the backrest isin the substantially vertical position.

Unless otherwise controlled by the motor 30, the first and secondmembers 1,2 are fixed relative to each other by the irreversibility ofthe mechanism. The hypocycloid mechanism 5 does not allow a torqueexerted on its output to create a force and torque sufficient to turnthe cam 9, thus ensuring irreversibility, and the first and second sideplates 1′, 2′ cannot rotate relative to each other and therefore thefirst and second members 1,2 can only move relative to each other whenso controlled by the motor, even during significant acceleration or animpact to the vehicle.

It should be noted that in this first embodiment, the first side plate1′ is connected to the backrest 71 and the second side plate 2′ isconnected to the seat part 72. Due to the relative hypocycloid movementof the first side plate in relation to the second side plate, with eachrevolution of the cam 9, the axis Y moves in a circle having a radiusequal to the eccentricity ‘e’ of the cam, but this movement of thebackrest relative to the position of the seat part is small in scale.

According to this first embodiment, there may be an auxiliary hingemechanism 5A arranged at the opposite side of the seat, which is theleft side in the example represented. This auxiliary hinge mechanism 5Ais simpler than the one described above, as it simply comprises ahypocycloid mechanism 5A, the latter being similar or identical to whathas been described. Said hypocycloid mechanism 5A is centered on Y andis controlled by an extension of the drive shaft 8, in a manner that issynchronous with the main hypocycloid mechanism 5 arranged on the rightside in the example shown.

According to a second embodiment of the invention (FIGS. 5-8), thepiezoelectric motor 30 and the reduction gearing 4 are arranged in anexternal area of the frame of the seat part, protruding outward on theright side and extending concentrically to axis Y.

The reduction gearing 4 comprises a first reduction stage formed by aplanetary gear train 61, and a second reduction stage formed by ahypocycloid mechanism 5, the latter being similar or identical to whatwas described for the first embodiment. Similarly, the piezoelectricmotor 30 is similar or identical to what was described for the firstembodiment, and a detailed description of these elements will thereforenot be repeated here.

As for the planetary gear train 61, it comprises, as is known from theprior art, a driving central gear 66, which meshes with the planetarygear teeth 67 on a planet carrier 68 engaging with a ring havingperipheral teeth 65. The reduction ratio of the planetary gear train 61may for example be between 6 and 12, and preferably about 10.

It should be noted that in this second embodiment, the first side plate1′ is connected to the seat part 72 and the second side plate 2′ isconnected to the backrest 71. Due to the relative hypocycloid movementof the first side plate in relation to the second side plate, with eachrevolution of the cam 8, axis Y remains stationary but the center of thesecond side plate 2′ moves along a circle having a radius equal to theeccentricity “e” of the cam, although this movement of the backrestrelative to the position of the seat part is small in scale. Thereduction ratio R is then 10 multiplied by 34, which is 340.

Still according to this second embodiment, there may also be anauxiliary hinge mechanism 5A arranged on the opposite side of the seat,controlled by the drive shaft 8 which extends from one side to theother.

In addition, in a variant not represented, the drive shaft 8 can passthrough the motor 30 when said motor is located within the inner spaceof the frame.

In a third embodiment of the invention (FIGS. 9 to 10), thepiezoelectric motor 30 is similar or identical to the above description.In contrast, the reduction gearing 4 comprises reduction gearing havinga single reduction stage. In this embodiment, the rotor 10 is directlycoupled to the drive shaft 8 which drives the cam 9 of a hypocycloidmechanism 50 similar in principle to the one already described.

However, in the example illustrated, the internal teeth 81 of the firstside plate comprises 330 teeth and the external teeth 82 of the secondside plate 2′ comprises 329 teeth. Each time the cam 9 completes arevolution, the second side plate 2′ is angularly offset by one toothrelative to the first side plate. Instead of one tooth, this could alsobe an offset of several teeth.

Still according to this third embodiment, there may also be an auxiliaryhypocycloid mechanism arranged at the opposite side of the seat,controlled in a synchronized manner by the drive shaft 8 which extendsfrom one side to the other. This auxiliary hypocycloid mechanismcomprises the same number of teeth as the hypocycloid mechanism 50described above for the third embodiment.

According to a fourth embodiment of the invention, illustrated in FIG.11, the piezoelectric motor 30 is similar or identical to the abovedescription, but the reduction gearing 4 comprises a single reductionstage, also known as an ‘inclined plane reduction gearing’, which willbe described below.

The first member 1 comprises a first ring gear 41, centered on the mainhinge axis Y, the tips of the teeth being perpendicular to the main axisY.

The second member 2 comprises a second ring gear 42, centered on themain axis Y and parallel to the first ring gear 41.

The reduction gearing comprises:

-   -   a drive member 12 rotationally guided about the main axis Y,        comprising an input shaft 11 and an inclined plane 12 a having a        normal X1 that is angularly offset relative to the main axis,    -   an intermediate transmission member 13 having a rear plane 13 a        in sliding contact with said inclined plane, a front        frustoconically-shaped portion centered on X1, supported by the        second member by means of a ball joint 16, a third ring gear 43        on the periphery of the frustoconical shape and engaging with        the first ring gear 41, and a fourth ring gear 44 adjacent to        the third ring gear 43 and engaging with the second ring gear        42.

When the rotor of the motor rotates, it causes the drive member 12 torotate and its normal X1 pivots about axis Y.

In a particularly preferred embodiment, the number of teeth on the thirdring gear 43 is less than the number of teeth of the first ring gear 41.Thus, when the drive member executes a complete revolution, theintermediate transmission member 13 is angularly offset relative to thehousing by one or more teeth depending on the difference in the numberof teeth, and this offset is in a first angular direction.

In addition, the number of teeth of the fourth ring gear 44 differs fromthe number of teeth of the second ring gear 42. Thus when saidintermediate transmission member 13 executes a complete revolution, theintermediate transmission member 13 is angularly offset by one or moreteeth depending on the difference in the number of teeth and for examplein an angular direction which may be the same as or may be opposite tothe first angular direction.

It is then possible to obtain a very high reduction ratio R, for examplewith the number of teeth being 20 and 19 respectively for the first andthird ring gears 41,43 and the number of teeth being 17 and 16respectively the second and fourth ring gears 42,44, which gives areduction ratio of 340.

Advantageously, in one aspect of the invention, the rotor shaft 10 andthe input shaft 11 may be formed of a single piece.

According to this fourth embodiment, there may also be a second‘inclined plane reduction gearing’ arranged on the opposite side andcontrolled in a synchronous manner by the drive shaft 8 which extendsfrom one side to the other.

It should be noted that the auxiliary hinge mechanism 5A arranged on theopposite side of the seat is optional and could be reduced to a simplepivoting connection.

It should also be noted that the hinge mechanism described above is notlimited to a hinge for a backrest and can be used for example byconsidering the seat element to be the seat part relative to the base,and in this case it is the height adjustment that is concerned; it canalso be used to pivot an element, such as the front edge of the seatcushion relative to the seat part or any other movable part of the seat.

Of course, a piezoelectric motor assumes the presence of an electroniccontrol unit, which is for example present on the circuit board 33; themechanism may additionally include a sensor, for example a Hall effectsensor, for capturing the position and/or speed of the rotor. Theelectronic control unit can use the information from the sensor tocontrol the stator 31.

It should also be noted that the use of a piezoelectric motor reducesthe electromagnetic emission levels in comparison to a DC motorsolution.

The invention claimed is:
 1. A hinge mechanism for vehicle seat, themechanism being adapted for connecting a first element of the seat to asecond element of the seat, the mechanism comprising: a first member forconnection to one of said first and second elements, a second member forconnection to the other of the first and second elements, mounted torotate about the first member on a hinge axis, reduction gearingarranged between an input member and the second member, said reductiongearing having a reduction ratio, a motor having a rotor rotatablysecured to said input member of the reduction gearing, for driving therotation of the second member relative to the first member through thereduction gearing, wherein the motor is a piezoelectric motor.
 2. Thehinge mechanism according to claim 1, wherein the reduction ratio of thereduction gearing is greater than or equal to 150, and wherein thepiezoelectric motor exhibits a rated rotational speed which is less than500 revolutions/min.
 3. The hinge mechanism according of claim 1,wherein the first element is a backrest of the seat and the secondelement is a seat part of the seat.
 4. The hinge mechanism according toclaim 1, wherein the piezoelectric motor exhibits a maximum torque whichis greater than 1 Newton-meter.
 5. The hinge mechanism according toclaim 1, further comprising an elastic biasing member adapted forapplying torque in a first direction, about the hinge axis, to thesecond member relative to the first member.
 6. The hinge mechanismaccording to claims 1, wherein the reduction gearing comprises a firstreduction stage formed of a planetary gear train, and a second reductionstage formed of a hypocycloid mechanism.
 7. The hinge mechanismaccording to claim 1, wherein the reduction gearing comprises a firstreduction stage formed of double reduction gearing, and a secondreduction stage formed of a hypocycloid mechanism.
 8. A motor vehicleseat comprising a hinge mechanism according to claim
 1. 9. The hingemechanism according to claim 1, wherein the reduction gearing has asingle reduction stage.
 10. The hinge mechanism according to claim 9,wherein the reduction gearing has a single reduction stage comprising asingle hypocycloid stage of at least 250 teeth.
 11. The hinge mechanismaccording to claim 1, wherein: the first member comprises a first ringgear, centered on the hinge axis, the second member comprises a secondring gear, centered on the hinge axis, the reduction gearing comprises:a drive member rotationally guided about the hinge axis, comprising aninput shaft and an inclined plane having an orthogonal direction that isangularly offset relative to the hinge axis, an intermediatetransmission member having a rear plane in sliding contact with saidinclined plane, a front portion supported by the second member, a thirdring gear engaging with the first ring gear, and a fourth ring gearengaging with the second ring gear.
 12. The hinge mechanism according toclaim 11, wherein the number of teeth of the third ring gear is lessthan the number of teeth of the first ring gear, and the number of teethof the fourth ring gear differs from the number of teeth of the secondring gear.
 13. The hinge mechanism according to claim 11, wherein arotor shaft and the input shaft are formed of a single piece.